Thermal transfer printer for film

Abstract

A thermal transfer printer for film capable of thermal transfer printing on a plastic film. The thermal transfer printer for film is provided with a conveyance for conveying the plastic film along a predetermined path, an ink ribbon moving mechanism which includes a holder for holding a plurality of ink ribbons 11 and moves an ink ribbon selected arbitrarily from the plurality of ink ribbons to a print position arranged on the predetermined path, and a print head which prints on the plastic film by heating the ink ribbon moved to the print position.

1. A thermal transfer printer for film, comprising:
 conveyance means for conveying a plastic film along a predetermined path; 
 an ink ribbon moving mechanism which includes holding means for holding a plurality of ink ribbons, moves an ink ribbon arbitrarily selected from the plurality of ink ribbons to a print position arranged on the predetermined path; 
 a print head which prints on the plastic film by heating the ink ribbon moved to the print position; 
 a platen roller which supports the ink ribbon and the plastic film from an opposite side of the print head; 
 a displacement preventing mechanism which brings the platen roller and the plastic film into close contact with each other such that the platen roller and the plastic film are not displaced from each other; 
 wherein a pinch roller which presses the plastic film against the platen roller is provided as the displacement preventing mechanism; and 
 a contact angle θ between the plastic film and the platen roller, backward tension T 1  generated in the plastic film in an opposite direction of a conveyance direction of the conveyance means, forward tension T 2  generated in the plastic film in the conveyance direction of the conveyance means, average tension T (=(T 1 +T 2 )/2) of the background tension T 1  and the forward tension T 2 , a difference in tension ΔT (=|T 1 −T 2 |/T) between the backward tension T 1  and the forward tension T 2 , force P with which the pinch roller presses the plastic film against the platen roller, and a dynamic friction coefficient μ between the platen roller and the plastic film satisfy the following formula (1):
   |2μT sin(θ/2)|+μP>Tx(1+ΔT)  (1) 
 
 (where θ=0 deg. to 180 deg.). 
 
   
   
     2. The thermal transfer printer for film according to  claim 1 , wherein the contact angle θ is set larger than 150 deg. 
   
   
     3. The thermal transfer printer for film according to  claim 1 , wherein the contact angle θ is set larger than 180 deg. and a diameter of the platen roller is larger than 100 mm. 
   
   
     4. A thermal transfer printer for film comprising:
 first conveyance means for conveying a plastic film; 
 second conveyance means for conveying a transfer member along a predetermined path; 
 an ink ribbon moving mechanism which includes holding means for holding a plurality of ink ribbons, and moves and ink ribbon arbitrarily selected from the plurality of ink ribbons to a print position arranged on the predetermined path; 
 a print head which prints on the transfer member by heating the ink ribbon moved to the print position; 
 a transfer mechanism which is arranged on a downstream side of the print position and transfers an image printed on the transfer member to the plastic film, 
 a platen roller which supports the ink ribbon and the transfer member from an opposite side of the print head; and 
 a displacement preventing mechanism which brings the platen roller and the transfer member into close contact with each other such that the platen roller and the transfer member are not displaced from each other, 
 wherein a pinch roller which presses the transfer member against the platen roller is provided as the displacement preventing mechanism; and 
 a contact angle θ T  between the transfer member and the platen roller, background tension T T1  generated in the transfer member in the opposite direction of a conveyance direction of the second conveyance means, forward tension T T2  generated in the transfer member in the conveyance direction of the second conveyance means, average tension T T (=(T T1 +T T2 )/2) of the backward tension T T1  and the forward tension T T2 , a difference in tension ΔT T (=|T T1 −T T2 |/T) between the backward tension T T1  and the forward tension T T2 , force P T  with which the pinch roller presses the transfer member against the platen roller, and a dynamic friction coefficient μ T  between the platen roller and the transfer member satisfy the following formula (2):
   |2μ T  sin(θ T /2)|+μ T P T >T T x(2+ΔT T )  (2) 
 
 (where θ T= 0 deg. to 180 deg.). 
 
   
   
     5. The thermal transfer printer for film according to  claim 4  wherein the contact angle θ T  is set larger than 150 deg. 
   
   
     6. The thermal transfer printer for film according to  claim 4 , wherein the contact angle θ T  is set larger than 180 deg. and a diameter of the platen roller is larger than 100 mm.